1. Field of the Invention
The present invention pertains to building systems and, more particularly, to a flexible building joint, providing a dynamic eave assembly for the structural intersection of angulated building members.
2. History of the Prior Art
The prior art is replete with structural building techniques which date back into technological antiquity. These structural systems generally incorporate a plurality of vertical, load bearing members, or wall sections, adapted for supporting siding disposed outwardly thereof and roof members thereabove. The support of a roof section necessitates the structural interengagement between the load bearing roof members, such as rafters and the wall members to comprise an eave. In many instances the structural roof members are angulated relative to the wall members for providing a slope to the roof surface facilitating the elimination of water from rain, snow and the like. Such designs are most typically seen in residential construction where pitched roofs have been commonplace for centuries. More conventional commercial construction has also adopted the "pitched roof" look in certain designs. Moreover, many commercial architectural innovations necessitate the utilization of angulated members for sloped side wall regions of buildings as well as roof sections thereon. The reasons vary but are basically founded upon the desire for distinction in both size and shape.
The introduction of angulated side and roof regions in commercial buildings has imposed additional structural and functional considerations. Conventional commercial construction generally utilizes a curtain wall system comprised of a plurality of planar glass sheets mounted upon vertical and horizontal mullions of generally hollow construction. The mullions are secured at various points to the structural members of the building and carry the weight of the glass panels disposed thereon as well as the responsibility for adequate sealing against water intrusion, drainage and structural integrity. Problems with the utilization of hollow mullions in angulated construction are, however, multifold. One problem is water intrusion, sealing and drainage. Another is purely structural, but even more serious. For example, the hollow mullions are fabricated from metal such as aluminum which is much more rigid than the wood which has been used for centuries in angulated roof/wall intersections. Loading of the roof from weight, rain, snow and the like will cause the angled roof members to deflect downwardly causing movement within the intersection. When the wall and roof members are mitered for mating engagement one to the other such deflection loads will cause high levels of compression across the inside edges of the contiguous mitered surfaces and separation forces across the outside mating region. The roof member in essence "pivots" against the vertical member. The inherent softness of wood generally used in residential construction absorbs this deflection load without serious damage to the joint. This is not the case when rigid metal sections are utilized because of the inherent structural rigidity and lack of elasticity to such compression loading. A welded mitered joint can, for example, ultimately manifest cracks along the weld due to the bending moment created through the rigid interengagement therebetween. The inside surfaces of the mitered joint resisting the deflection load serves as a pivot point, or fulcrum, across which the bending forces are amplified toward the outside intersection.
The stress problems of angular intersections have been addressed with gusset plates. The plates are usually conformed to the angle of the intersection and then bolted, welded, or riveted to the structural members. Although gusset plates have found widespread utility, they are both expensive and often unsightly. This has not been a favorite mode of expression because it can appear more like a riveter's handiwork than an architect's innovative design. Conventional attempts have thus been made to make the structural intersection joint not only practical but better looking than the present mode of expression. Current designs thus include a curved profile utilizing either clear plexiglass or a radius tempered insulated glass. The problem with plexiglass is that it is not scratch resistant, is difficult to maintain and often must be replaced within a short period of time due to wear. The radius tempered glass whether of the insulated or noninsulated variety is far more permanent, but is extremely expensive. This creates numerous sealing, handling and installation problems.
Appearance, construction ease and economics are typically the strong considerations in conventional construction of the curtain wall variety. For this reason it would be beneficial to provide a flexible joint structure which does not produce the deleterious bending forces of conventional designs and can facilitate water drainage. The method and apparatus of the present invention provides such an improvement over the prior art through a dynamic eave construction. The assembly utilizes a flexible joint across which a gap is provided preventing the abutting engagement of the inside surfaces of the angulated structural members during loading. Drainage ears on the upper rafter empty water behind the sealant and into the vertical mullion. In one embodiment a pivot pin is included within the joint for transmitting the structural load directly from the roof member to the vertical mullion and facilitating the pivotal interaction therebetween in a manner not detrimental to the structural integrity of the joint. Moreover, the flexible joint can be provided in an aesthetically pleasing configuration without the appearance of gusset plates, welds and the like.